refactor(geschichte): add utils.ts (formatAuthorName/DisplayName/PublishedAt), update README

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/geschichte/utils.ts

@@ -0,0 +1,28 @@
+import { formatDate } from '$lib/shared/utils/date';
+
+type AuthorSummary = { firstName?: string; lastName?: string; email: string };
+type AuthorView = { displayName: string };
+
+/** Format an author name from a list summary (firstName + lastName, falling back to email). */
+export function formatAuthorName(author: AuthorSummary | null | undefined): string {
+	if (!author) return '';
+	const full = [author.firstName, author.lastName].filter(Boolean).join(' ').trim();
+	return full || author.email || '';
+}
+
+/** Format an author displayName from a detail view. */
+export function formatAuthorDisplayName(author: AuthorView | null | undefined): string {
+	return author?.displayName ?? '';
+}
+
+/**
+ * Format a publishedAt ISO string to a localised date string.
+ * Returns null when publishedAt is absent.
+ */
+export function formatPublishedAt(
+	publishedAt: string | null | undefined,
+	style: 'short' | 'long' = 'short'
+): string | null {
+	if (!publishedAt) return null;
+	return formatDate(publishedAt.slice(0, 10), style);
+}